Pr autolabel pr template

[ARPANPATRA111]

• added .github/PULL_REQUEST_TEMPLATE.md so contributors must fill a structured PR template with linked issues, summary, testing steps, screenshots, and ai disclosure.
• added .github/workflows/validate-pr-template.yml which checks if PR is done right or not. (according to the PR template)
• added sync-pr-issue-labels.yml the label-sync logic so it reads every closing issue reference in the PR and copies the union of all issue labels to the PR
• added cleanup logic so every label is removed when a PR is closed without being merged

Screenshots or recordings

what will this workflow do ?

1. It checks whether contributors actually followed the PR template.
2. It copies all labels from every linked closing issue to the PR.
3. It removes all labels from a PR if that PR is closed without merge.

Known limitations

• if issue labels change after the PR has already been labelled, the PR will not automatically resync until the PR is edited or another tracked PR event happens
• if linked issues are changed later, previously synced labels are not automatically removed unless the PR is closed without merge
• if maintainers use issue labels that they do not want copied to PRs, this workflow will still copy them because it now mirrors every issue label

Closes #76

[vercel]

@ARPANPATRA111 is attempting to deploy a commit to the vaibhav's projects Team on Vercel.

A member of the Team first needs to authorize it.

[ARPANPATRA111]

@Vaibhav-kesarwani Done with #76👍